Filler selection

Impurities in natural sources can result in poor color, lower retention of physical properties on long-term heat aging, and reduction in electrical properties with the presence of electrolytes. Therefore, fine precipitated ATH and magnesium hydroxide are favored as particle size can be controlled to a nominal 1 pm size with low surface area and they contain very low impurity levels. Magnesium hydroxide production processes, by manufacturer, have considerably more variation than ATH but both metal hydrates are considered products by process, which in many cases results in the need to qualify alternate sources or in some cases to reformulate around filler selection. 

Fillers are used in these products to improve mechanical properties or impart flammability resistance. Fillers are frequently silane-treated to further improve mechanical properties. Fillers must have a low moisture (below 0.1%), a low absorption of resin, and are expected to impart thixotropic properties. There are special cases. For example, if peroxyketals are used as initiators, basic fillers have to be used because acidic fillers interfere with cure times and the shelf-life of the composition. Shape and particle size distribution must be considered in filler selection to impart the desired rheological properties. Calcium carbonate is the most popular filler but aluminum trihydrate, anhydrous calcium sulfate, and silica are also frequently used. Barite is well suited to this application, especially if acid... 

Fillers are often useful in epoxy-polyamide adhesives (41). Fillers aid flow control—particularly at elevated temperatures. Other properties contributed by fillers are exhibited in the cured system. For example, they can increase the modulus of elasticity, modify the coefficient of thermal expansion, increase heat resistance, and even affect bond strength. Of course, the excellent wetting properties of polyamides Increase the dispersion efficiency of these fillers. The type of filler selected and the amount used also have a pronounced effect on adhesive quality. A few of these effects are illustrated in Tables VI and VII (37). (See also Table VIII.)... 

Filler Selection. General-purpose photometers tie supplied with several filters, ejich oi which transmits a different portion of the visible spcctruiii. Selection of... 

Fillers increase the strength, impart needed rheological properties, and reduce the cost of sealants. Tensile properties are increased significantly, depending on the type of filler, its particle size, and the type of cure. Improper filler selection can ruin the performance of a polysulfide sealant. Calcium carbonates (wet or dry ground limestone, precipitated), carbon blacks (furnace, thermal), calcined clays, silica and silicate fillers, and rutile titanium dioxide are typical fillers used in polysulfide sealants. Generally, combinations of fillers are used in formulation. Plasticizers improve the working properties while... 

Mineral fillers used are calcium carbonate (CaCOj), China Clay (Al/0H [Si.,0 J), miea especially muscovite (KAyOHjFlJAlSijOj J), silica flour (SiO ), talc (Mg, (OH)j[Si Oj J), and wollastonite (CaSiOj). Parameters that need to be considered during inorganic filler selection are basicity, filler impurities that may influence the resin euring proeess, and filler hardness that eauses abrasion of the mold [1]. Mica filled phenolics are used in electrical parts because mica adds outstanding dielectric properties, high thermal and chemical resistance and low water absorption [1]. 

Greatest improvement is achieved by using the largest practical concentration of fillers and by using fillers having highest thermal conductivity. Filler particle size and distribution is also a factor. Technical and practical reasons determine the filler selection and filled plastic formulation. 

The conductivity of the final product may vary greatly, depending upon the metallic filler selected, the particle size, shape, previous history and the amount used. With non-noble metals, the surface of the filler particles has to be cleaned to remove non-conducting surface oxides. With certain metallic fillers these oxides can gradually re-form, reducing the conductivity as the material ages. 

BAGASSE-RUBBER COMPOSITE DEVELOPMENT Composite Filler Selection... 

As an extra illustration of the versatility of the latex-based concept, not only in terms of the choice of the polymer matrix [see Chapter 5], but also regarding the filler selection, graphene-nanocomposites were prepared by latex-technology. ... 

Filler selection can be critical to the performance of the finished product and should be given careful consideration. 

Q. Zhao, S. Bahadur (1999) The mechanism of filler action and the criterion of filler selection for reducing wear, Near 225-229,660. 

Filler selection and loading level are very important in formulation of adhesive because adhesive properties depend on filler type, size, shape, and volume contents. Common fillers are metal powder, kind of clay, dust, glass fiber, alumina, and so on. Sometimes fillers act as extenders or reinforcement materials. 

The filler efficiency and the corresponding material endurance depend on many parameters. The filer type, the amount used, the particle size selected and the degree of bonding to the polymer matrix are some of them to be considered. In the case of ATH, which is the filler selected in many formulations, much research has been done in the direction of the optimum formulation that will conclude in an increased material performance and lifetime. 

Polymeric blends and nanocomposites are an effective method for producing materials with new or improved properties. However, these enhanced characteristics often depend not only on the type of filler selected, but also on the dispersion achieved. Unfortimately, conventional processes often fail to achieve high levels of dispersion without strenuous processing, solvent, or material modification. In addition, concerns over environmental impact such as use of renewable versns non-renewable resources and the cost of synthrtic polymers have recently motivated significant research in snpport of snstainable polymo- systems in which one or more component is biodegradable and bio-based. These materials inclnde agro-polymers, snch as starch, and biode adable polyesters, snch as poly(caprolactone) (PCL) and poly(lactic acid) (PLA). 

---